Extensible boom with tandem operating cylinders



July 5, 1966 R. E. STAUFFER' EXTENSIBLE BOOM WITH TANDEM OPERATINGCYLINDERS Filed Dec.

5 Sheets-Sheet 1 July 5, 1966 R. E. STAUFFER EXTENSIBLE BOOM WITH TANDEMOPERATING CYLINDERS Filed Dec. 26, 1963 5 Sheets-Sheet 2 N WUN w Om R mm7 T A N i W Msq July 5, 1966 R. E. STAUFFER EXTENSIBLE BOOM WITH TANDEMOPERATING CYLINDERS 5 Sheets-Sheet 3 Filed Dec.

INVENTOR;

ROBERT ESTAUFF'ER, BY

July 5, 1966 R. E. STAUFFER 5 SheetsSheet 4.

Filed Dec.

INVENTOR,

ROBERT ESTAUFFER) 9 lo 3 m mm m t K a cl 2 1 y 7 l: f rlo 5 if" H 6 80H& m5 2v m 2 0d 5 n m 1 L aw r76 3 Q July 5, 1966 R. E. STAUFFER3,259,251

EXTENSIBLE BOOM WITH TANDEM OPERATING CYLINDERS Filed Dec. 26, 1965 5Sheets-Sheet 5 ow. Q I; .Q/

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INVENTOR; ROBERT E.5TAUFFER, BY 1 Q L United States Patent 3,259,251EXTENSIBLE BOOM WITH TANDEM OPERATING CYLINDERS Robert E. Stautfer,Galion, Ohio, assignor to Jeffrey Galion Manufacturing Company, acorporation of Ohio Filed Dec. 26, 1963, Ser. No. 333,322 10 Claims.(Cl. 21255) The instant invention relates to cranes, and moreparticularly, to improved operating means for the operation of elementsof such cranes.

It is an object of this invention to provide an improved operating meansfor extending and retracting an extensible crane boom.

It is another object of this invention to provide an improved operatingmeans for extending and retracting a crane boom, in which such operatingmeans includes several operating devices which act together to extendand retract the crane boom, whereby the load on an individual operatingdevice is reduced.

It is a further object of the instant invention to provide an improvedoperating means for extending and retracting a crane boom comprisingseveral cylinder and piston mechanisms connected in tandem for extendingand retracting the crane boom, the length of movement of the boom beingthe sum of the lengths of movement of the cylinder and pistonmechanisms.

Still another object of the instant invention is to provide an improvedoperating means for extending and retracting a crane boom comprisingcylinder and piston mechanisms, that is of a simplified construction.

Other objects of the invention willappear hereinafter, the novelfeatures and combinations being set forth in the appended claims.

In the drawings:

FIG. 1 is a side elevational view of a crane constructed in accordancewith the instant invention;

FIGS. 2A and 2B together are an elevational sectional view of the boomin extended position;

FIGS. 3A and 3B together are a top plan view of the boom in extendedposition;

FIGS. 4A and 4B together are an elevational sectional view of the boomin retracted position;

FIG.- 5 is a sectional view of the boom, taken on the line 55 in FIG.2A.

FIG. 6 is a sectional view of the boom, taken on the line 66 in FIG. 2A;

FIG. 7 is a sectional view of the boom, taken on the line 77 in FIG. 2B;

FIG. 8 is a sectional view of the boom, taken on the line 8-8 in FIG.2B;

FIG. 9 is a sectional view of the cylinder and piston mechanisms forextending and retracting the boom;

FIG. 10 is a top plan view of the adjacent ends of the cylinder pistonmechanisms;

FIG. 11 is a side elevational view of the lower end of the lowercylinder and piston mechanism; and

FIG. 12 is a plan view of the upper boom supporting roller.

Referring to the drawings, particularly FIG. 1, there is illustratedtherein a crane 20, which is constructed in accordance with, andembodies the instant invention. The crane 20, which is illustratedherein by way of example, is commonly referred to as a portable ormobile hydraulic crane, by reason of the fact that it is a selfpropelled machine that may be driven under its own power, and theoperating system for the crane mechanisms is of the hydraulic type.

The crane 20 has a main frame or chassis 21 which is mounted on frontwheels 22 and rear wheels 23, all of which are driven for propulsion ofthe crane 20. Both the front wheels 22 and the rear wheels 23 aresteerable to provide the crane 20 with a high degree of mobility. At therear of the chassis 21 there is provided an engine 24, which providesthe power for driving the crane 20, including the hydraulic operatingsystem for the various crane mechanisms. At the front of the chassis 21there is provided an operators station 25 at which there are placed thevarious controls 28 for the crane 20.

At the front of the chassis 21 there is provided a pair of Outriggers26, and likewise, at the rear there is provided a pair of Outriggers 27,which are alike in all respects. The outriggers 26, 27 at the front andrear extend to opposite sides of the chassis 21, and may be lowered intobearing contact with the ground, as illustrated in FIG. 1, to provideadded support for the crane 20 and thereby to stabilize it.

A pedestal 30 is disposed in a substantially centrally located positionon the chassis 21 and extends upwardly therefrom. The pedestal 30supports the boom assembly 31, and is rotatable in opposite directionson the chassis 21 about an upright axis, whereby the boom assembly 31may be swung continuously in a full circle. The boom assembly 31 ispivotally mounted on the pedestal 30 and may be raised and lowered, asillustrated in FIG. 1. The boom assembly 31 includes a lower boom 32 andan upper boom 33, the latter being telescoped within the former, andbeing extensible and retractable relatively to the lower boom 32,whereby the boom assembly 31 may be lengthened and shortened, as needed,to reach various places where it is desired to either pick up or setdown a load. At the outer end of the upper boom 33 there is a hook block34 which depends from the end of the upper boom 33 on a cable 35. Awinch is supported on the end of the lower boom 32 for paying out andtaking up the cable 35 to raise and lower the book block 34 as required.

The pedestal 30 comprises laterally spaced side plates 39 which aresecured to a turntable base plate 40 having a circular configuration.

The laterally spaced side plates 39 of the pedestal 30 extend upwardlyand rearwardly and terminate in overhanging mounting arms on which theboom assembly 31 is pivotally mounted. A pivot pin 86 extends lateral ybetween the opposite arms 85 of the side plates 39 and through the lowerboom 32, whereby the pivot pin 86 pivotally connects the boom assembly31 to the pedestal 30. A lift cylinder and piston mechanism 87 has itscylinder end secured to the turntable base plate 40 by a pin 88, and itspiston rod end is secured to the lower boom 32 by a pin 89. The liftcylinder and piston mechanism 87 is disposed in an upright positionbetween the turntable base plate 40 and the boom assembly 31, betweenthe opposite side plates 39. The lift cylinder and piston mechanism 87may be extended to raise the boom assembly 31 by swinging it upwardly onthe pivot pin 86, and contracted to lower the boom assembly 31 byswinging it downwardly. The lift cylinder and piston mechanism 87 isoperated by hydraulic fluid under pressure that is supplied thereto formoving its piston and piston rod upwardly and downwardly within thecylinder 87.

The lower boom 32 is formed with a box-like construction having asubstantially rectangular cross section, as seen in FIGS. 5, 6 and 7.The upper boom 33 is similarly provided with a box-like constructionhaving a substantially rectangular cross section, as seen in FIGS. 6, 7and 8, and is smaller in sectional dimension than the lower boom 32 topermit the upper boom 33 to be received within the lower boom 32 by atelescoping action of the upper boom 33 into the lower boom 32.Operating means is provided for extending and retracting the upper boom33 with respect to the lower boom 32, thereby adjusting the length orrea ch of the boom assembly 31. Such adjustment of the boom assembly 31may be made in any position thereof, whereby the crane has a high degreeof flexibility in its operation.

Heretofore, reference has been made to the lower boom 32 and the upperboom 33. The use of the terms lower and upper for the respective booms32, 33 is accepted usage, and derives from the fact that the boomassembly 31 most often is disposed in an upwardly extending position inwhich the upper boom 33 is above the lower boom 32. In the interest ofconsistency, the terms lower and upper will be used herein withreference to other elements of the boom assembly 31, to describe therelative dispositions thereof.

A pair of laterally spaced posts are secured to the lower end of thelower boom 32. A cylinder and piston mechanism 91 has its cylinder 92formed with an car 93 at the lower end thereof. The cylinder ear 93 isdisposed between the posts 90 and is secured thereto by a transverse pin94, as seen in FIG. 7. A suitable universal bearing 95 is interposedbetween the pin 94 and the cylinder car 93. The pin 94 is secured to theposts 90 by a pair of nuts 96, 96, which are turned on the oppositethreaded ends of the pin 94. Thus, the cylinder 92 has its lower endanchored to the lower end of the lower boom 32.

The lower end of the cylinder 92 has a port 96 through which hydraulicfluid under pressure is delivered to the lower end of the cylinder 92 toapply force to the piston 97 and to move it and its piston rod 98upwardly of the cylinder 92, thereby extending the cylinder and pistonmechanism 91. A second port 99 for hydraulic fluid under pressure isalso located at the lower end of the cylinder 92 above the first port86. A line 100 connects the second port 99 to a port 101 at the upperend of the cylinder 92. Hydraulic fluid under pressure is suppliedthrough the port 99, the line 100 and the port 101 to the upper end ofthe cylinder 92 to apply force to the piston 97 to move it and itspiston rod 96 downwardly in the cylinder 92, thereby contracting thecylinder and piston mechanism 91.

The piston rod 98 is formed of an outer tubular member 102 and an innertubular member 103, which are concentrically disposed with respect toeach other, and are spaced one from the other. The lower end of theouter tubular member 102 is secured to the piston 97 by a nut 109. Thelower end of the inner tubular member 103 is mounted within the outertubular member 102 in spaced relation thereto by an annular spacer 104,which forms a seal between the lower ends of the outer and inner tubularmembers 102, 103. The upper end of the outer tubular member 102 issecured to a connector block 105, and the inner tubular member 103 isalso secured to the connector block 105 in concentric speed relation tothe outer tubular member 102.

The lower end of the outer tubular member 102 has several ports 106which connect to the annular space 107 that is formed between the outerand inner tubular members 102, 103. The connector block 105 has a port108 that connects to the annular space 107 at the upper end of thepiston rod 98. The hydraulic fluid under pressure, which is supplied tothe cylinder 92 through the port 101, flows through the ports 106, theannular passage 107 and to the port 108. A port 110 is centrallydisposed in the nut 109 and connects to the lower end of the passage 111that extends the length of the inner tubular member 103. The connectorblock 105 has a port 112 that connects to the upper end of the passage111. The hydraulic fluid under pressure which is supplied to the lowerend of the cylinder 92 through the port 96 flows through the port 110and the passage 111, to the port 112.

The connector block 105 is formed with an ear 115, by which the lowercylinder and piston mechanism 91 is connected to the upper cylinder andpiston mechanism 116. The cylinder 117 of the upper cylinder and pistonmechanism 116 has a clevis 113 at its lower end, in which the car 115 isreceived. The ear 115 is connected to a transverse pin 119 by a suitableuniversal bearing 120, as seen in FIG. 6. The pin 119 extends toopposite sides of the ear 115 and through the clevis 118, with the pin119 being secured to the clevis 118 by opposite nuts 121, 121, turned onthe threaded portions of the pin 119 and bearing against the oppositesides of the clevis 118. This articulated connection of the lowercylinder and piston mechanism 91 to the upper cylinder and pistonmechanism 116 is flexible on the pin 119, to permit relative movementbetween the respective cylinder and piston mechanisms 91, 116.

A line 122 has one end connected to the port 112 of the connector block105, and its other end is connected to the port 123 at the lower end ofthe cylinder and piston mechanism 116. Hydraulic fluid under pressureflows from the port 112 through the line 122 to the port 123 and intothe lower end of the cylinder 117 to act on the piston 124- to move itand its piston rod 125 upwardly of the cylinder 117 to extend thecylinder and piston mechanism 116. By reason of the connections betweenthe cylinder and piston mechanisms 91, 116, they are both extended atthe same time, and in addition, the cylinder 11,7 of the upper cylinderand piston mechanism 116 has an upward translatory movement, since it isconnected to the upper end of the piston rod 98 and moves therewith.

A line 126 has one end connected to the port 108 of the connector block105, and its other end is connected to a port 127 at the upper end ofthe cylinder 117. Hydraulic fluid under pressure flows from the port 108through the line 126 and through the port 127 into the upper end of thecylinder 117 to act on the piston 124 to move it and its piston rod 125downwardly of the cylinder 117 to contract the cylinder and pistonmechanism 116. By reason of the connections between the lower and uppercylinder and piston mechanisms 91, 116, they are contracted both at thesame time, and in addition, the cylinder 117 has a downward translatorymovement.

The upper end of the piston rod 125 has an car 128, by which the uppercylinder and piston mechanism 116 is connected to the upper boom 33. Theear 128 is connected to a transverse pin 129 by a suitable universalbearing 130, as seen in FIG. 8. Oppositely disposed mounting blocks 131,131 are secured to the side walls of the upper boom 33, and extendinwardly therefrom to the ear 128. Each mounting block 131, 131 has abore within which there is received a spacer 132. The transverse pin 129extends through the opposite spacers 132, 132 and is secured to themounting blocks 131, 131 by nuts 133, 133 which are turned on theopposite threaded ends of the pin 129, with washers 134, 134 beinginterposed between the nuts 133, 133 and the spacers 132, 132, tothereby secure the pin 129 to the upper boom 33.

Thus, the assembly, including the lower cylinder and piston mechanism 91and the upper cylinder and piston mechanism 116, is connected to thelower end of the lower boom 32 and to the upper boom 33 near the upperend thereof, whereby extension of the cylinder and piston mechanisms 91,116 extends the upper boom 33 with respect to the lower boom 32, andlikewise, contraction of the cylinder and piston mechanisms 91, 116retracts the upper boom 33 with respect to the lower boom 32.

At the upper end of the lower boom 32, there is a transverse pin whichextends laterally between the side walls of the lower boom 32 and issecured thereto, as seen in FIG. 7. The pin 140 is disposed below theupper boom 33, and supports a pair of mounting blocks 141, 141 that arejournaled on the pin 140. Each mounting block 141 has a flat upperfaceon which there is secured a wear plate 142, which is formed of asuitable bearing material, such as bronze. Each wear plate 142 issecured to its mounting block 141 by a pair of bolts 143, 143 disposedone on each side of the transverse pin 140. The upper boom 33 isslidably supported by the wear plates 14-2, 142. Under load, the lowerand upper booms 32, 33 are subject to bending, and in order toaccommodate to the same, the wear plates 142, 142 and their mountingblocks 141, 141 are journaled on the transverse pin 140 so that theupper boom 33 is properly supported by the wear plates 142, 142. Thus,the wear plates 142 always have a full surface contact with the underside of the upper boom 33.

At the upper end of the lower boom 32, and at each side thereof, thereis a wear plate 144 which is secured to a side wall of the lower boom 32by a pair of bolts 145, 145. Several spacers 146 are interposed betweeneach Wear plate 144 and the side wall of the lower boom 32 to properlylocate the wear plates 144, 144 in a transverse direction, so as to bearagainst the sides of the upper boom 33 and to maintain it in atransversely centered position within the lower boom 32. The wear plates144, 144 are preferably formed of a bearing material, such as bronze, sothat the upper boom 33 will be easily slidable on the wear plates 144,144, as it moves outwardly and inwardly with resepect to the lower boom32.

A pair of wear plates 147, 147 is secured to the top of the upper boom33 at the lower end thereof. The wear plates 147, 147 are secured bybolts 148, 148 and bear against the top wall of the lower boom 32. Thewear plates 147, 147 are preferably formed of a bearing material, suchas bronze, so that they are freely slidable on the top wall of the lowerboom 32 as the upper boom 33 moves upwardly and downwardly relatively tothe lower boom 32.

A wear plate 149 is secured to each side of the upper boom 33 at thelower end thereof. Each wear plate 149 is secured by bolts 150, 150 withseveral spacers 151, 151 interposed between a side wall of the upperboom 33 and a wear plate 149 to properly locate the latter in atransverse direction for centering the upper boom 33 transversely withinthe lower boom 32. The wear plates 149, 149 bear against the side wallsof the lower boom 32 and are preferably formed of a bearing material,such as bronze, so that the upper boom 33 will be freely slidablerelatively to the lower boom 32. When the boom assembly 31 supports aload at its upper end, the force at the lower end of the upper boom 33causes it to bear against the top wall of the lower boom 32, and suchforce is resisted by the wear plates 147, 147. When the boom assembly 31is swung in a circle the forces acting on the upper boom 33 tend to moveit laterally relatively to the lower boom 32. Such lateral movement ofthe upper boom 33 is resisted by the wear plates 149, 149 at the lowerend of the upper boom 33, and the wear plates 144, 144 at the upper endof the lower boom 32.

At the lower end of the upper boom 33 there is an arm 154, which ismounted adjacent the bottom wall of the upper boom 33 and extendsrearwardly therefrom. The arm 154 is pivotally mounted on the side wallsof the upper boom 33 by a pair of opposite pins 155, 155. A roller 156is rotatably supported on one end of the arm 154 beyond the end of theupper boom 33. The roller 156 rides on the bottom wall of the lower boom32. A11 adjusting bolt 157 is threaded through the other end of thepivoted arm 154 and abuts the bottom wall of the upper boom 33 to adjustthe position of the arm 154 and the roller 156. When the upper boom 33is retracted into the lower boom 32, and there is no load on the boomassembly 31, the weight of the upper boom 33 would tend to cause thelower end thereof to drop down on the bottom wall of the lower boom 32.However, the roller 156 supports the lower end of the upper boom 33 sothat it maintains its central position spaced above the bottom wall ofthe lower boom 32.

Within the upper boom 33 there are provided two supporting bars 160,160, which are secured to the side walls thereof by a plurality of bolts161, there being one such supporting bar 160 at each side of the upperbom 33. Each supporting bar 160 extends longitudinally along the upperboom 33 from the lower end thereof through a distance that iscommensurate with the translatory movement of the upper cylinder andpiston mechanism 116,

such movement being equal to the travel of the piston 97 and piston rod98 of the lower cylinder and piston mechanism 9 1. The transverse pin119 by which the cylinder and piston mechanisms 91, 116 are connected toeach other, has opposite ends 162, 162 which extend to adjacent theopposite supporting bars 160, 160, as seen in FIGS. 6 and 10. On eachpin end 162 there is pivotally mounted a slide 163, which has a channelconfiguration to fit over the supporting bar 160, Thus, the engagementof the slides 163-, 163 with the supporting bars 160, provides a supportfor the flexible or articulated joint between the cylinder and pistonmechanisms 91, 116 in all positions thereof. As the joint, which isrepresented by the pin 1-19, moves upwardly and downwardly with respectto the boom assembly 31, the slides 163, 163 ride along the supportingbars 160, 161 and maintain engagement therewith. When the boom assembly31 is supporting a load, there is some bending thereof. The flexibleconnection of the cylinder and piston mechanisms 91, 116, including thepin 119, permits such bending of the boom assembly 31 to occur withoutthe same being transmitted to the cylinder and piston mechanisms 91, 116to any degree that will alfect the operation thereof. Since the slides163, 163 are journaled on the ends 162, 162 of the pin 119, theseelements do not interfere with the flexibility of the connection betweenthe cylinder and piston mechanisms 91, 116.

At the lower end of the lower boom 32 there is secured a counterweight165 for the purpose of connterbalancing the loads supported on the endof the boom assembly 31. The counterweight 165 is U-shaped in plan view,and within the counterweight 165 there is placed the winch 36 having awinch drum 167, on which there is Wound the cable 35. The winch 36 isdriven by a hydraulic motor 169. A roller is disposed above the winchdrum 167 in contact with the cable 35. Leaf springs 171, 171 are securedto the ends of the axle 172 of the roller 170 and to ears 173, 173 atthe top of the lower boom 32. The leaf springs 171, 171 press the roller170 down on the windings of the cable 35 on the winch drum 167, wherebythe cable 35 will be properly payed in and out from the winch 36. Theroller 170 prevents the condition of the cable 35 merely uncoiling onthe winch drum 167, rather than being payed out. When winding the cable35 on the winch drum 167, the roller 170 assures that the cable 35 istightly wound thereon.

The cable 35 extends from the winch drum 167 to a boom head 174 at theupper end of the upper boom 33. The boom head 174 includes a pluralityof sheaves 175, over which the cable 35 is reeved to a hook block 34,which likewise includes a plurality of sheaves 177, over which the cable35 is reeved. The hook block 34 has a depending hook 178 by which a loadmay be engaged to be lifted and moved by the crane 20.

The crane embodying the operating means as described herein operatessmoothly and efliciently. The boom assembly is intended to liftsubstantial loads, and these subject the boom assembly to severe stress.Notwithstanding such loading, the upper boom may be extended andretracted easily by the upper and lower cylinder and piston mechanisms,the operation of which is not impeded by the boom loads.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from the spirit andscope of the invention as defined by the claims hereto appended, andapplicant therefore wishes not to be restricted to the preciseconstruction herein disclosed.

Having thus described and shown an embodiment of the invention, what itis desired to secure by Letters Patent of the United States is:

1. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first power unit and a second power unitarranged in tandem to apply the force of both power units to extend andretract the upper boom, and a flexible joint connection located betweensaid power units and disposed in line with the tandem arrangement ofsaid power units for connecting said power units to each other wherebysaid power units are yieldable relatively to each other.

2. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable power unitand a second extensible and retractable power unit, said first andsecond power units being disposed along the upper and lower booms intandem to apply the force of both power units to extend and retract theupper boom and the extensive and retractive movement of the upper boombeing commensurate with the extensive and retractive movements of bothpower units, and a flexible joint connection located between said powerunits and disposed in line with the tandem disposition of said powerunits for connecting said power units to each other whereby said powerunits are yieldable relatively to each other.

3. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, and aflexible joint connection located between said cylinder and pistonmechanisms and disposed in line with the tandem disposition of saidcylinder and piston mechanisms for connecting said cylinder and pistonmechanisms to each other whereby said cylinder and piston mechanisms areyieldable relatively to each other.

4. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, a fluidconnection to said first cylinder and piston mechanism for supplyingfluid thereto under pressure to actuate the first piston and piston rodthereof, a fluid connection through said first piston and piston rod tosaid second cylinder and piston mechanism for supplying fluid theretounder pressure to actuate the second piston and piston rod thereof, andmeans connecting said cylinder and piston mechanisms to each othercomprising an articulated joint connecting the piston rod of said firstcylinder and piston mechanism to said second cylinder and pistonmechanism whereby said cylinder and piston mechanisms are yieldablerelatively to each other.

5. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, meanssecuring the first cylinder and piston mechanism to the lower boom andmeans securing the second cylinder and piston mechanism to the upperboom, and articulated joint means located between said cylinder andpiston mechanisms and disposed in line with the tandem disposition ofsaid cylinder and piston mechanisms for connecting said cylinder andpiston mechanisms to each other whereby said cylinder and pistonmechanisms are yieldable relatively to each other.

6. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable power unitand a second extensible and retractable power unit, said first andsecond power units being disposed along the upper and lower booms intandem to apply the force of both power units to extend and retract theupper boom and the extensive and retractive movement of the upper boombeing commensurate with the extensive and retractive movements of bothpower units, a flexible connection for connecting said power units toeach other whereby said power units are yieldable relatively to eachother, and said upper boom including supporting means in engagement withsaid flexible connection in all positions of the power units and of theupper boom to support the power units.

7. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, a flexibleconnection for connecting said cylinder and piston mechanisms to eachother whereby said cylinder and piston mechanisms are yieldablerelatively to each other, and said upper boom including supporting meansslidably engaged with said flexible connection in all positions ofextension and retraction of the cylinder and piston mechanisms and ofthe upper boom to support the cylinder and piston mechanisms.

8. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, anarticulated joint connecting an end of one cylinder and piston mechanismto an end of the other cylinder and piston mechanism whereby saidcylinder and piston mechanisms are yieldable relatively to each other, asupporting bar on the upper boom extending along the upper boom, a slideconnected to the articulated joint and slidably engaged with thesupporting bar to support the articulated joint and the adjacent ends ofthe cylinder and piston mechanisms in all positions of extension andretraction of the cylinder and piston mechanisms and of the upper boom.

9. A crane structure comprising, a lower boom and an upper boom in whichthe upper boom is adapted to be extended and retracted relatively to thelower boom, power means for extending and retracting said upper boom,said power means including a first extensible and retractable cylinderand piston mechanism and a second extensible and retractable cylinderand piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, a pivot pinconnecting an end of one cylinder and piston mechanism to an end of theother cylinder and piston mechanism to form an articulated joint betweensaid cylinder and piston mechanisms whereby the are yieldable relativelyto each other, a supporting bar secured to the upper boom and extendingalong the line of movement of the articulated joint as the cylinder andpiston mechanisms are extended and retracted, a slide pivotally mountedon said pivot pin and complementally formed with respect to saidsupporting bar to be slidably engaged with said supporting bar and tosupport the articulated joint and the adjacent ends of the cylinder andpiston mechanisms on the supporting bar in all positions of extensionand retraction of the cylinder and piston mechanisms and of the upperboom.

10. A crane structure comprising, a lower boom and an upper boom inwhich the upper boom is adapted to be extended and retracted relativelyto the lower boom, power means for extending and retracting said upperboom, said power means including a first extensible and retractablecylinder and piston mechanism and a second extensible and retractablecylinder and piston mechanism, said first and second cylinder and pistonmechanisms extending along the upper and lower booms and being disposedin tandem to apply the force of both cylinder and piston mechanisms toextend and retract the upper boom and the extensive and retractivemovement of the upper boom being commensurate with the extensive andretractive movements of both cylinder and piston mechanisms, 2. fluidconnection to the cylinder of the first cylinder and piston mechanismfor supplying fluid thereto under pressure to actuate the piston andpiston rod thereof, a fluid connection through the first piston andpiston rod to the cylinder of the second cylinder and piston mechanismfor supplying fluid thereto under pressure to actuate the piston andpiston rod thereof, means for securing one end of the first cylinder andpiston mechanism to the lower boom and means for seeming one end of thesecond cylinder and piston mechanism to the upper boom, the other endsof the cylinder and piston mechanisms being disposed adjacent eachother, a pivot pin connecting the adjacent ends of the cylinder andpiston mechanisms to form an articulated joint between said cylinder andpiston mechanisms whereby they are yieldable relatively to each other, asupporting bar secured to the upper boom and extending along the line ofmovement of the articulated joint as the cylinder and piston mechanismsare extended and retracted, a slide pivotally mounted on said pivot pinand complementally formed with respect to said supporting bar to beslidably engaged with said supporting bar and to support the articulatedjoint and the adjacent ends of the cylinder and piston mechanisms on thesupporting bar in all positions of extension and retraction of thecylinder and piston mechanisms and of the upper boom.

References Cited by the Examiner UNITED STATES PATENTS 2,551,246 5/1951DArcey 91-167 2,568,228 9/ 1951 Forse 92-51 X 2,903,142 9/1959 Wills21266 2,969,042 1/r1961 Litz et a1 92-51 X 3,044,635 7/ 1962 Kirsten 2123,051,323 8/ 1962 Kuhlenschmidt 212--35 3,093,248 6/1963 Winter 212553,103,281 9/ 1963 Rumsey et al 212-66 3,154,199 10/1964 'Balogh et a1.21235 SAMUEL F. COLEMAN, Primary Examiner.

A. LEVINE, Assistant Examiner.

1. A CRANE STRUCTURE COMPRISING, A LOWER BOOM AND AN UPPER BOOM IN WHICHTHE UPPER BOOM IS ADAPTED TO BE EXTENDED AND RETRACTED RELATIVELY TO THELOWER BOOM, POWER MEANS FOR EXTENDING AND RETRACTING SAID UPPER BOOM,SAID POWER MEANS INCLUDING A FIRST POWER UNIT AND A SECOND POWER UNITARRANGED IN TANDEM TO APPLY THE FORCE OF BOTH POWER UNITS TO EXTEND ANDRETRACT THE UPPER BOOM, AND A FLEXIBLE JOINT CONNECTION LOCATED BETWEENSAID POWER UNITS AND DISPOSED IN LINE WITH THE TANDEM ARRANGEMENT OFSAID POWER UNITS FOR CONNECTING SAID POWER UNITS TO EACH OTHER WHEREBYSAID POWER UNITS ARE YIELDABLE RELATIVELY TO EACH OTHER.